While these are welcome and substantial improvements, I find myself continually baffled by the trend of putting messenger functionality in everything. App fatigue is real and I feel like we’re just perpetuating it.

You’re not wrong, but the value here isn’t an attempt to add “me-too” features to Nextcloud, from my understanding. The goal with Nextcloud Talk is to be able to have that messenger functionality in an entirely self-hosted place without relying on third parties. And Nextcloud is starting to develop a network effect significant enough that tying the messenger to Nextcloud is also valuable, instead of embedding XMPP/IRC/Matrix. (Though there is work being done to bridge Nextcloud and XMPP that I’m looking forward to.)